In using a continuous sucker rod string in a well, it is known to use an injector to inject into or pull the rod from the well. U.S. Pat. No. 3,559,905 by Palynchuk discloses a method and apparatus for running and pulling a continuous metal member into and out of a well. The apparatus uses a pair of opposed driven endless tracks provided with gripping pads to grip the continuous metal member between the pads and pull it out of the well. The gripping pads comprise an elastomeric element having poor wear resistance and providing a poor grip on the member when the member is dirty.
Other types of injectors used for the different application of conveying coiled tubing are described in U.S. Pat. No. 6,609,566 by Perio Jr., U.S. Pat. No. 6,332,501 by Gipson, U.S. Pat. No. 5,975,203 by Payne et al., and U.S. Pat. No. 6,189,609 by Shaaban et al. and U.S. Pat. No. 6,173,769 by Goode. Typically gripping pads are formed of elastomeric material, polymers or graphite composites to prevent damage to the tubing. In general these types of gripping elements have poor wear resistance and must be replaced frequently at great cost. The poor wear resistance is unsuitable for use with a metal sucker rod. In some instances the gripping members comprise steel or tungsten carbide, however the hardness of these metals would cause considerable damage and wear to the metal finish of a typical sucker rod.
In some instances the gripper members comprise integral blocks mounted onto the drive chains so that replacement of the blocks requires separation of the block by disassembly of the chain at considerable expense of time and cost. In other instances the gripper members include replaceable elements, however the manner of supporting the replaceable elements typically provides minimal structure for adequately transferring drive forces from the drive chains to the rod string being conveyed.